Tibor Nagy - PHY 231 Fall 2019 1Practice Exam #2

Nagy,

Tibor

Keep this exam CLOSED until advised by the instructor.

50 minute long closed book exam.

Fill out the bubble sheet: last name, first initial, student number (PID). Leave the section, code, form andsignature areas empty.

Two two-sided handwritten 8.5 by 11 help sheets are allowed.

When done, hand in your test and your bubble sheet.

Thank you and good luck!

Posssibly useful constant:

• g = 9.81 m/s2

Posssibly useful Moments of Inertia:

• Solid homogeneous cylinder: ICM

= (1/2)MR2

• Solid homogeneous sphere: ICM

= (2/5)MR2

• Thin spherical shell: ICM

= (2/3)MR2

• Thin uniform rod, axis perpendicular to length: ICM

= (1/12)ML2

• Thin uniform rod around end, axis perpendicular to length: Iend

= (1/3)ML2

Tibor Nagy - PHY 231 Fall 2019 2Practice Exam #2

nagytibo@msu

Please, sit in row G.

1 pt Are you sitting in the seat assigned?

1.A Yes, I am.

Tibor Nagy - PHY 231 Fall 2019 3Practice Exam #2

3 pt A crane at a construction site lifts a concrete block with a mass of m = 442 kg from the ground to the top of

a building with a height of h = 15.9 m. How much work did the motor of the crane do? (Assume zero energy loss inthe lifting mechanism due to friction.)(in J)

2. A 6.10× 104

B 6.89× 104

C 7.79× 104

D 8.80× 104

E 9.95× 104

F 1.12× 105

G 1.27 × 105

H 1.44× 105

3 pt If the duration of the lift was 2.90 minutes, then what was the average power performed by the crane?

(in W)

3. A 1.88× 102

B 2.73× 102

C 3.96× 102

D 5.75× 102

E 8.33× 102

F 1.21× 103

G 1.75× 103

H 2.54× 103

Tibor Nagy - PHY 231 Fall 2019 4Practice Exam #2

4 pt An ideal spring is fixed at one end. A variable force F pulls on the spring. When the magnitude of F reaches a

value of 31.9 N, the spring is stretched by 16.0 cm from its equilibrium length. Calculate the additional work requiredby F to stretch the spring by an additional 10.3 cm from that position.(in J)

4. A 4.34 B 5.78 C 7.68 D 1.02× 101

E 1.36× 101

F 1.81× 101

G 2.40× 101

H 3.20× 101

Tibor Nagy - PHY 231 Fall 2019 5Practice Exam #2

4 pt A 631 kg automobile slides across an icy street at a speed of 41.2 km/h and collides with a parked car which has

a mass of 985 kg. The two cars lock up and slide together. What is the speed of the two cars just after they collide?(in km/h)

5. A 1.61× 101

B 2.01× 101

C 2.51× 101

D 3.14× 101

E 3.93× 101

F 4.91× 101

G 6.14× 101

H 7.67 × 101

Tibor Nagy - PHY 231 Fall 2019 6Practice Exam #2

3 pt A 62.5 kg wood board is resting on very smooth ice in the middle of a frozen lake. A 48.5 kg boy stands at one

end of the board. He walks from one end of the board to the other end with a velocity of 1.91 m/s relative to the icein the positive direction. What is the velocity of the board relative to the ice?(in m/s)

6. A -2.05 B -1.76 C -1.48 D -0.697

E 0.697 F 1.48 G 1.76 H 2.05

Tibor Nagy - PHY 231 Fall 2019 7Practice Exam #2

3 pt Select True or False for the following statement.

⊲ The center of mass of an extended object is always located within the material of the object.7. A True B False

Tibor Nagy - PHY 231 Fall 2019 8Practice Exam #2

The graph shows the x-displacement as a function of time for a particular object undergoing simple harmonic motion.

−3

−2

−1

0

1

2

3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

x (m

)

t (s)

This function can be described by the following formula:x(t) = Asin(ωt), where x and A are measured in meters, t is measured in seconds, ω is measured in rad/s.

3 pt Using the graph determine the amplitude A of the oscillation.

(in m)

8. A 1.20 B 1.80 C 2.10 D 2.40 E 3.60 F 4.20 G 4.50 H 4.80

3 pt Determine the period T of the oscillation.

(in s)

9. A 2.80 B 3.60 C 4.00 D 5.20 E 5.60 F 6.40 G 6.80 H 7.60

3 pt If the mass of the object is 48.5 g, then what is the total mechanical energy of this oscillator?

(in J)

10. A 1.55× 10−1

B 2.25× 10−1

C 3.26× 10−1

D 4.72× 10−1

E 6.85× 10−1

F 9.93× 10−1

G 1.44 H 2.09

Tibor Nagy - PHY 231 Fall 2019 9Practice Exam #2

3 pt An extended body (not shown in the figure) has its center of mass (CM) at the origin of the reference frame.

In the case below give the direction for the torque τ with respect to the CM on the body due to force F acting on thebody at a location indicated by the vector r.

⊲

11. A X B -X C Y D -Y E Z F -Z

Tibor Nagy - PHY 231 Fall 2019 10Practice Exam #2

4 pt Three small objects are located in the x-y plane as shown in the figure. All three objects have the same mass,

m = 1.99 kg.

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6 7 8 9

y (

m)

x (m)

A

B

C

What is the moment of inertia of this set of objects with respect to the axis perpendicular to the the x-y plane passingthrough location x = 5.00 m and y = 4.00 m? (The objects are small in size, their moments of inertia about their owncenters of mass are negligibly small.)(in kg*m^2)

12. A 2.06× 101

B 2.40× 101

C 2.81× 101

D 3.29× 101

E 3.85× 101

F 4.51× 101

G 5.27 × 101

H 6.17 × 101

Tibor Nagy - PHY 231 Fall 2019 11Practice Exam #2

3 pt You are going to back out of a driveway. You put your car in reverse and you start driving backwards. The

driveway is straight and horizontal. What is the direction of the velocity vector of your car?

13.A to your leftB up to the skyC down to the groundD to your rightE backwardF The velocity is zero.G forward

3 pt What is the direction of the angular velocity vector of your wheels?

14.A backwardB The angular velocity is zero.C to your leftD to your rightE down to the groundF up to the skyG forward

Tibor Nagy - PHY 231 Fall 2019 12Practice Exam #2

An object with a mass of m = 119 kg is suspended by a rope from the end of a uniform boom with a mass of M = 67.3kg and a length of l = 7.77 m. The end of the boom is supported by another rope which is horizontal and attached tothe wall as shown in the figure.

θm

lM

3 pt The boom makes an angle of θ = 58.3◦ with the vertical wall. Calculate the tension in the vertical rope.

(in N)

15. A 3.06× 102

B 3.83× 102

C 4.78× 102

D 5.98× 102

E 7.47 × 102

F 9.34× 102

G 1.17 × 103

H 1.46× 103

4 pt Calculate the tension in the horizontal rope. (The horizontal and the vertical ropes are not connected to each

other. They are both independently attached to the end of the boom.)(in N)

16. A 3.29× 102

B 4.38× 102

C 5.83× 102

D 7.75× 102

E 1.03× 103

F 1.37 × 103

G 1.82× 103

H 2.42× 103

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